Theory, phenomenology, and experimental avenues for dark showers: a Snowmass 2021 report

Abstract

In this work, we consider the case of a strongly coupled dark/hidden sector, which extends the Standard Model (SM) by adding an additional non-Abelian gauge group. These extensions generally contain matter fields, much like the SM quarks, and gauge fields similar to the SM gluons. We focus on the exploration of such sectors where the dark particles are produced at the LHC through a portal and undergo rapid hadronization within the dark sector before decaying back, at least in part and potentially with sizeable lifetimes, to SM particles, giving a range of possibly spectacular signatures such as emerging or semi-visible jets. Other, non-QCD-like scenarios leading to soft unclustered energy patterns or glueballs are also discussed. After a review of the theory, existing benchmarks and constraints, this work addresses how to build consistent benchmarks from the underlying physical parameters and present new developments for the pythia Hidden Valley module, along with jet substructure studies. Finally, a series of improved search strategies is presented in order to pave the way for a better exploration of the dark showers at the LHC.

Dark Sector Showers in the Lund Jet Plane

“…Isolating these different stages allows us to explore the impact of each effect on the structure of the LJP. 1 At each stage of the simulation, large-radius (R = 1.0) anti-k t jets [62] are clustered from the partons or hadrons using Fastjet [63,64]. Jets are required to have p t > 1000 GeV.…”

“…This paradigm has received tremendous attention in recent years; our interest here is exploring the implications for Large Hadron Collider (LHC) phenomenology, e.g. see the Snowmass study [1].…”

Report of the Topical Group on Physics Beyond the Standard Model at Energy Frontier for Snowmass 2021

“…As a result, specialized strategies are needed, as reviewed in detail in [427]. While major progress was made of the last few years, theoretical and experimental challenges remain: On the theory front, more order in the vast space of model building space is needed to arrive at a comprehensive set of recommendations.…”

“…This may be achieved by imposing additional theory prior, developing simplified models or both. Further Monte Carlo development also remains needed, though a major step forward was made in [427]. On the experimental side, one must continue to innovate with analysis strategies, both online and offline, and critically examine when isolation criteria and/or p T threshold could potentially be relaxed in exchange for a higher number of LLPs in the event.…”

“…These portals have been taken as the starting point for building benchmarks leading to dark showers signatures in the contributed whitepaper in Ref. [427] and summarized in previous Section 11. 3.4. In the following section 12.4.2, we will focus on qualitative and conceptual aspects of including a dark matter candidate in HV models and dark showers, as discussed in the Dark Showers project meeting in May 2022.…”